Apparatus for detecting an ignition arc and controlling a burner



1956 w. F. MILLER APPARATUS FOR DETECTING 0N IGNITION ARC ANDCONTROLLING A BURNER Filed Feb. 24, 1954 INVENTOR. WILL/AM MILLER ATTORNE Y United States Patent 6 i APPARATUS FOR DETECTING AN IGNITIGNARC AND CGNTROLLENG A BURNER William F. Miiler, Youngstown, OhioApplication February 24, 1954, Serial No. 412,244

1 Claim. (Cl. 15823) This invention relates to apparatus forautomatically determining whether or not an ignition arc, such as usedfor igniting fuel delivered by an oil burner, is operating.

The principal object of the invention is the provision of apparatus fordetecting an ignition arc.

A further object of the invention is the provision of apparatus fordetecting an electric arc and particularly an are employed as ignitionmeans in connection with an oil burner wherein air and oil areintroduced into a combustion area.

A still further object of the invention is the provision of apparatusfor detecting an ignition arc and controlling an oil burner or similardevice to prevent operation of said oil burner or similar device at suchtimes as the ignition arc is not functioning.

A still further object of the invention is the provision of apparatusfor detecting an ignition are which utilizes infrared radiation of thearc and more particularly energy pulsations of the are.

A still further object of the invention is the provision of apparatusfor detecting an ignition are through the use of a photocell scanning arestricted target area adjacent a straight path between the electrodessupporting the arc to detect the energy pulsations of the arc varyingfrom said straight path as occurs during the normal operation of an oilburner.

The apparatus for detecting an ignition are disclosed herein is ofparticular value in supervising the operation of an oil burner andparticularly an oil burner in a relatively large industrial installationwhere a considerable volume of vaporized oil may be introduced into acombustion area in a relatively short time.

Those skilled in the art will recognize that many commercial oil burnerinstallations in operation at the present time introduce several gallonsof oil in atomized form in a relatively few seconds and that the absenceof an ignition are from the precise moment of starting the introductionof the fuel may result in a highly dangerous volume of explosive air andfuel mixture.

It has heretofore been believed impossible to detect the actual ignitionarc utilized in such oil burner installations quickly enough to preventthe introduction of a dangerous quantity of vaporized fuel into theassociated equipment. Those skilled in the art will appreciate thatindustrial oil burning equipment and usage has therefore been denied thesafety factor that has existed with gas burning equipment inasmuch asapparatus for instantaneous detection of pilot flames has been availableand widely used.

The present invention utilizes a lead-sulphide photocell responsive to apulsating infrared radiation. The lead-sulphide photocell is unlike therectifying types of photocells commonly used for detecting oil flames asthe lead-sulphide photocell is most sensitive to infrared radiation,which energy striking the cell reduces its electrical resistance andthus changes the voltage across the cell. The pulsations of energytherefore vary the cell resistance and set up small fluctuations involtage. These 2,771,942 Patented Nov. 27, 1956 ICC fluctuations producethe effect of an A.-C. voltage signal of mixed frequencies.

In a typical installation utilizing the herein disclosed apparatus, thelead-sulphide photocell is used in connection with an adapter comprisinga tuned amplifier having a maximum response to a signal ofapproximately-l3 cycles from the photocell. The amplifier converts theA.-C. signal to a small DC. signal which is suflicient to actuate arelay controlling the fuel source of the controlled installation.

The photocell is focused on a small target area immediately adjacent astraight path between the tips of the ignition arc electrodes of theequipment supervised so that an arc following a straight path betweenthe electrodes is out of the target area whereas fluctuations in thearc, as are common and which are due in part to air introduced alongwith the fuel charge adjacent the ignition electrodes, cause the arc tomove alternately into and out of the target area.

Fluctuations of the are thus occur in the target area as long as the arcexists and the detection of the arc is therefore possible and theassociated equipment enabled to control the fuel source in the absenceof the arc and thereby prevent the introduction of explosive mixtures inthe absence of an ignition arc.

With the foregoing and other objects in view which will appear as thedescription proceeds, the invention resides in the combination andarrangement of parts and in the details of construction hereinafterdescribed and claimed, it being the intention to cover all changes andmodifications of the example of the invention herein chosen for purposesof the disclosure, which do not constitute departures from the spiritand scope of the invention.

The invention is illustrated in the accompanying drawing, wherein:

Figure 1 is a symbolic illustration of an air andoil delivering sectionof an oil burner together with the ignition electrodes adjacent theretoand illustrates the po.- sitioning and scanning area of adetection'photocell.

Figure 2 is an end view of the apparatus of Figure 1 showing thescanning area adjacent a straight ignition arc path.

Figure 3 is an end view of the apparatus shown in Figure 1 showing indotted lines the normal fluctuation of an ignition arc into and out ofthe photocell scanned area.

Figure 4 is a symbolic diagram illustrating the target and apparatuscontrolled by the photo-electric cell.

By referring to the drawings and Figure l in particular, it will be seenthat a wall 10 of a combustion area is indicated and that a tubularmember or air blast tube 11 is positioned therethrough so as to extendinto said combustion area. An oil delivering pipe 12 extends into thearea of the tubular member 11 and terminates with a nozzle tip 13through which atomized oil or other suitable fuel 14 is introduced. Thetubular member or air blast tube 11 provides a passageway for theintroduction of air into the combustion area.

Electrodes 15 and 16 covered throughout the majority of their length byporcelain insulators 17 and 18 extend alongside the oil delivering pipe12 and terminate adjacent the nozzle tip 13 and in spaced relation toone another.

The electrodes 15 and 16 are downturned at their outermost ends andangularly positioned with respect to one another so that their outermostends or tips are more closely spaced to one another than the remainingportions thereof. When a suitable source of electrical energy isconnected with the electrodes 15 and 16, a suitable ignition arc isestablished between the tips of the electrodes, as indicated by thedotted lines in Figures 2 and 3 of the drawings. 7

The structure just described will be recognized by those skilled in theart as being conventional and it will occur to those skilled in the artthat if the introduction of oil and air takes place through the airblast tube 11 and the nozzle tip 13 and the ignition arc isnotestablished across the tips of the electrodes 15 and 16, there will be aresulting creation of a highly explosive fuel laden atmosphere.

In order that this cannot occur, a photocell 19 responsive to pulsatinginfrared radiation and, preferably of the lead-sulphide type, is mountedin the wall in alignment with a focusing tube 29, which may or may notbe provided with a restricted orifice 21, so that the area scanned bythe photocell 19 will comprise a small area immediately between theelectrode porcelains 17 and 18 and just above a straight path betweenthe tips of the electrodes and 16.

The straight path is illustrated by dotted lines A in Figure 2 of thedrawings and the scanned'target area is indicated by a dotted circularline S in Figure 2 of the drawings.

At such time as a source of electrical energy is connected with theelectrodes 15 and 16 and an ignition arc established on the dotted lineA, it will characteristically fluctuate from the straight path of thedotted line to the bowed paths A, AB and AC, as shown in Figure 3 of thedrawings. It will be observedrthat the bowed path AB is well within thescanning area S of the photocell 19 while the paths A and AC are not.-

The fluctuation of the are from the straight path A to the bowed pathsAB and AC occurs continuously when air is being introduced 'throughtheair blast tube 11 by the equipment of the oil burner or the like andfrequently occurs in the absence of such introduction of air. The aretherefore fluctuates with respect to its presence or absence in thescanning area S and is thereby capable of effectively actuating thephotocell 19 with the resultant change of voltage across the cell. 7 i

As the pulsations of the existing ignition arc vary, the photocell 19resistance will establish small fluctuations in voltage in a circuitthrough the photocell 19. Such small fluctuations in voltage areconveyed to a tuned amplifier 22, as illustrated in Figure 4 of thedrawings, and converted thereby to a small D.-C. signal which isconveyed to a relay 23 which in turn is connected with the solenoidvalve 24 in the fuel supply pipe 12 for the efiective control thereof.

Those skilled in the art will recognize that the amplifier 22 and therelay 23 require electric energy for their operation and areillustrated'in Figure 4 of the drawings as connected with a suitable v.power source.

The specific equipment is available commercially and includes thelead-sulphide photocell, the tuned amplifier and the relay and theinvention relates to utilizing said radiant energy fluctuation responsephotocell and associated equipment with an ignition arc to enablethe'safety control of oilburner equipment and the like..

It will thus be seen that the herein disclosed method of detecting anigntion arc enables an oil burner installation dependent on an ignitionare for operation to be effectively supervised so that no oil will beintroduced into the combustion area unless the-ignition arc is firstestablished and its existence determined by the photocell 19 scanningthe normal fluctuation area of the ignition arc.

. Having thus described my invention, what I claim'is:

A burner control system including a burner having an outlet, fueldelivery means for said burner and ignition electrodes at said outlet, aphotocell responsive to fluctuations of radiant energy positioned toscan only an area to one side of a straight path between the tips ofsaid ignition electrodes whereby said photocell receives fluctuations ofradiant energy caused by the movement of an ignition are into and out ofsaid area, a circuit including an electrically operable valvecontrolling said fuel delivery means, a tuned amplifier having an inputcircuit connected to said photocell and selectively responsive to thefrequencies of said fluctuations, a power source for said amplifier, arelay including a coil con nected to an output circuit of said amplifierfor actuation by the output current of said amplifier upon occurence ofsaid fluctuations, a power source for said valve circuit, said relayhaving a switch in said circuit controlling said valve.

References Cited in the file of this patent UNITED STATES PATENTS2,208,386 Null July 16, 1940 2,228,997 Sparrow Jan. 14, 1941 2,398,008Isserstedt -1" Apr. 9; 1946 2,405,807 Arant Aug. 13, 1946 2,469,664Mnrch May 10, 1949 2,506,192 Beckett May 2, 1950 2,692,962 Thomson Oct,26. 1954

